Naoki is the eldest of the Tachibana siblings.
He has black hair, black pants, socks and shoes with a blue tie and a white dress shirt. In his poster for their TV show, he had on a plane white T-shirt and tan long pants.
He is the boy that Misaki had when she had sex in the alleyway at the arcade. Naoki bore witness to his mother getting punched in the face while engaged to her first husband with his sister, Akiho. They, alone with their younger brother and sisters, Jiyun and Sachi have had to raise their youngest brother, Takahiro, due to their mother's negligence. Because of this, he has become bitter.